Serial homicide cold cases present some of the most formidable challenges in modern criminal investigation due to behavioral variability, jurisdictional fragmentation, and forensic limitations. These cases often involve marginalized victims, span decades, and are hindered by incomplete data and investigative discontinuity. This chapter explores the evolving landscape of serial homicide investigations, highlighting both persistent barriers and transformative innovations. Particular focus is given to forensic investigative genetic genealogy (FIGG), which has revolutionized cold case resolutions by identifying offenders long thought beyond reach. Drawing on case studies including the Golden State Killer and William Talbott II, the chapter underscores the power of emerging technologies, national databases like ViCAP and CODIS, and collaborative efforts with nonprofit organizations. Ethical and legal implications of FIGG are examined, along with policy recommendations aimed at standardizing data sharing, improving evidence preservation, and ensuring victim-centered justice. Together, these insights chart a path forward for resolving serial homicide cold cases with greater equity, efficiency, and accountability.